Skrutskie explained that such stellar occultations occur when a celestial body—like a planet, moon, or asteroid—passes in front of a distant star, momentarily blocking its light. "By timing that event with millisecond accuracy, one can gain precise details about the size, shape, and atmosphere of the occulting object," he noted, highlighting how this method offers spatial detail that surpasses even the most advanced telescopes on Earth or in space.
Occultation of Pluto Brings UVA Researchers to South Africa
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Occultation of Pluto Brings UVA Researchers to South Africa
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n August 4, 2024, the shadow of Pluto swept across the Earth cast by a star 500 times fainter than the eye can detect. As it happened, UVA Astronomy professor Michael Skrutskie staffed a brand new a new 0.5-meter Hubble Optics telescope in the middle of the Kalahari Desert in South Africa. Skrutskie was part of a six-person team, which also included four UWC faculty and students and fellow UVA Professor Anne Verbiscer. The team had spent about a week in Cape Town setting up the telescope, donated by UVA to UWC, before heading 500 miles north to view the occultation. In the approximately one-second-long event, they gained invaluable information about Pluto and its atmosphere.
The path of the center of Pluto's shadow across South Africa on August 4. The red dot marks the researchers' observing location.
The endeavor of chasing occultations is not only scientifically rewarding but also serves as a valuable team-building exercise. Observers must position themselves at a precise location on Earth, typically within 100 meters, to capture the event at an exact predetermined time. "If you are one second late, you've wasted a trip around the world," Skrutskie remarked, underscoring the challenges and precision required for such observations.
Recognizing the logistical challenges and costs of shipping telescopes to remote locations, UVA has pivoted towards establishing permanent observational setups. "It has become more cost-effective to purchase and base a new telescope permanently in the country of interest," Skrutskie explained. The growing collaboration between UVA and UWC provides a natural opportunity to nurture long-term scientific and educational partnerships, supported by the new telescope. The resources of UWC Professor Nico Orce’s MANDELA nuclear detector laboratory were also essential, both as a home for setting up the telescope and, more importantly, for the facilities they had available – 3D printing in particular – to make final modifications to the telescope to prepare for the occultation expedition.
Left: A faint star to the right of a brighter star before Pluto’s occultation, Right: Pluto occulting the faint star (image is blurred due to a sudden gust of wind)
Skrutskie described the UWC collaboration as extraordinary. “At every level – students, faculty, administrators – everyone was both incredibly enthusiastic about the work and tremendously friendly and welcoming,” he said, noting their willingness to work on and practice with the telescope system at all hours. UVA's own occultation group, consisting of motivated undergraduates, regularly participates in local observations around Charlottesville. This group, which has recently become a registered student organization, actively trains new members to become experts in occultation work, demonstrating a growing interest and engagement in this field.
Looking ahead, Skrutskie emphasized the exciting opportunities for future collaborations. "Our future is entirely in the stars—literally," he commented. He is currently working with the UWC team to prepare for their first solo mission—an occultation of a bright star by Neptune on October 9, which will offer a rare chance to observe Neptune's rings and atmosphere. Remarkably, this event will also be visible from Virginia, enabling a transatlantic collaboration between UVA and UWC students and researchers. With several high-value occultation events occurring every year that are observable from South Africa, Skrutskie is enthused about the potential for more student exchanges and joint scientific endeavors in the future.
